Cushion and self-adjusting valve

ABSTRACT

A cushion with a support pad comprising a plurality of compressible suspension elements with a cover top and bottom joined together to form an impervious barrier, and a valve in fluid communication with the plurality of compressible suspension elements that allows the controlled expulsion of air until a user positioned on the cushion is optimally immersed in the cushion. When the user is removed from the cushion, the valve allows ingress of air into the cushion. In one aspect, the valve comprises an expansion valve controls air flow out of and into the cushion. In one aspect, the valve comprises a labyrinth seal that dampens air flow and pressure spikes. The valve comprises a pressure responsive compression spring that controls the expulsion of air from the cushion and, consequently, adjusting the immersion depth of the seated user.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application Ser.No. 61/408,774, filed Nov. 1, 2010, which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

The invention relates generally to support surfaces that facilitateblood flow and prevent tissue breakdown and more particularly to acushion that has relatively uniform restoring forces when deformed underloads from of a user and to a valve that can be employed with thecushion to vent air when the user is seated to achieve desired,predetermined immersion into the cushion to provide optimum seatingcharacteristics including uniform restoring forces.

Individuals confined to sitting, for example in a wheelchair run therisk of tissue breakdown and the development of ischemia induced sores,which are extremely dangerous and difficult to treat and cure. Forexample, when seated much of the individual's weight concentrates in theregion of the ischia, that is, at the bony prominence of the buttocks,and unless frequent movement occurs, the flow of blood to the skintissue in these regions decreases to the point that the tissue breaksdown. When lying down, the hip region may protrude deeper into themattress than the adjoining waist or thigh regions and as a consequencethe supporting forces exerted by the mattress would be greater at thehips than at the thighs or waist, for example. Any skin area where thereis sustained deformation suffers reduced blood flow and the skin doesnot receive sufficient oxygen and nutrients.

It is desirable to have a support surface that applies generally uniformsupporting forces, for example, a generally uniform counter force on thetissue of the ischial area of user positioned on a cushion. When acushioning structure is deformed while supporting a person, it isdesirable to have a constant restoring force that exerts equal forcesover a broader area of the body minimizing deformation of the softtissues and help prevent skin and tissue breakdown by facilitating bloodflow in the contacted area.

Cellular cushions generally provide the most uniform distribution ofweight and thus provide the greatest protection from the occurrence ofpressure sores. Inflatable cellular cushions have an array of closelyspaced air cells that project upwardly from a common base. Within thebase the air cells communicate with each other, and thus, all exist atthe same internal pressure. Hence, each air cell exerts essentially thesame restoring force against the buttocks, irrespective of the extent towhich it is deflected. U.S. Pat. No. 4,541,136 shows a cellular cushioncurrently manufactured and sold by assignee, ROHO, Inc. of Belleville,Illinois, for use on wheelchairs.

A variation of the cellular cushion provides isolated zones and alsowith cells of varying height. By varying the volume of air betweenzones, for example, one can accommodate for skeletal deformities whilestill maintaining satisfactory protection against pressure sores. U.S.Pat. No. 4,698,864 shows zoned cellular cushion with cells of varyingheight. U.S. Pat. No. 5,163,196 and U.S. Pat. No. 5,502,855 discloseother zoned cellular cushions having isolated inflation zones.

Two types of valves used to maintain air volume in the inflation zonesare shown in U.S. Pat. No. 6,687,936 and U.S. Pat. No. 6,687,936. Thesevalves, which can be referred to broadly as slide valves, when employedfor example with a zoned cushion having a plurality of inflation zones,provide an easily manipulated valve assembly which can be used to allowfluid communication between two or more zones or can be used to isolatethe zones.

Each valve, in general, includes a casing having an internal bore and aplurality of openings along the length of the casing that open into thebore. The openings are connected to the individual inflation zones viatubing or the like to place the bore of the casing in communication withthe inflation zones. The valve also includes a movable slide seatedsnugly within the casing bore. The slide can be manipulated to align thediscrete air chambers with the casing openings so as to functionallyalign the slide openings with the casing openings to allow the inflationzones to communicate and the air to flow to and from the variousinflation zones through the valve slide bore. The cushion is inflatedand the user positioned on the cushion. Air is released from a fillvalve until the user reaches optimum immersion. The slide is manipulatedto move the slide openings and the casing openings out of alignment,thereby sealing off the inflation zones and maintaining the individualinflation zones at optimum internal pressure.

Zoned cellular cushions with slide valves have become an industrystandard and work exceptionally well for there intended purposes. Aswill be understood, users of these cushions and valves, or theircaregivers, require some training and practice at setting the desiredimmersion dept and seating position. Although the needed proficiency intheir use is not difficult to obtain, there are some circumstances inwhich a user could benefit from a support surface, such as a cushion oreven a mattress or mattress overlay, that is even simpler or moreconvenient to use that these cushion and valve combinations. Thesecircumstances can arise, for example, where the user is newly disabledand perhaps overwhelmed by the attendant change in lifestyle. Or, forexample, if the user just does not have the mental acumen to properlyuse an adjustable cushion. An example may be a person suffering fromdementia or Alzheimer's.

It would therefore be advantageous to have a support surface, such as acushion or mattress, with a self-adjusting valve that allows a user reston the support surface and reach an optimal immersion level without themanipulation of a valve or the like.

SUMMARY OF THE INVENTION

In one aspect, a cushion with a support surface comprising a pluralityof compressible support elements, and a valve in fluid communicationwith the plurality of compressible suspension elements that allows thecontrolled expulsion of air until a user positioned on the cushion isoptimally immersed in the cushion and also controls dampens dynamic airflow and pressure spikes resulting from movement of the seated user.

In one aspect, a cushion with a support surface comprises a support padwith a plurality of compressible suspension elements that when the usergets off of the cushion, the support pad returns the cushion to theoriginal cushion height and the valve allows ingress of air into thecushion.

In one aspect, the valve comprises an expansion valve design, throughmultistage pressure reduction, which dampens the dynamic air flow andpressure spikes that result from movement of the seated user.

In one aspect, the valve comprises a labyrinth seal design, throughmultistage pressure reduction, which dampens the dynamic air flow andpressure spikes.

In one aspect, the valve comprises a pressure responsive compressionspring that controls the expulsion of air from the cushion and,consequently, controls the immersion depth of the seated user.

In one aspect, the cushion comprises a cover bottom under the supportsurface; the preferred embodiment of the cover bottom is a polyurethanefilm.

In one aspect, the cushion comprises a cover top over the supportsurface; the preferred embodiment of the cover top is a polyurethanefilm.

In an alternative embodiment, the cover top over the support surface canhave fabric bonded to the polyurethane film, providing a cover top overthe support surface that is easily cleaned by wiping down with a mildcleaning solution.

In one aspect each suspension element has a displaceable, load-bearingsurface, a first end wall, a second end wall, and an optional bottomwall. The load bearing surface, end walls and bottom wall, if present,define an inner chamber. The material thickness of the load-bearingsurface is greater than the material thickness of the end walls so thatthe end walls can distend outwardly when force is applied to saidload-bearing surface. Optionally, a top wall can include a vent openingformed therein of a predetermined size that allows controlled release ofair from each chamber when force is applied to the load bearing surfaceto control collapsing of the cell.

In one aspect, the support surface of the cushion is displaceable suchthat, when deformed, the suspension elements exert a restoring forcethat is generally constant irrespective of the extent of the deflection.The cushion applies distributed supporting pressure against anirregularly contoured body area, such as the ischium, supported on thecushion.

In one aspect of the cushion the array of suspension elements isarranged in a pattern wherein the longitudinal axis of each suspensionelement is positioned at a right angle relationship to the longitudinalaxis of the adjacent suspension elements. The right angle axis positionof the suspension elements improves stability imparted to the user.

In one aspect of the cushion the load-bearing surface has a generallyarch-like cross-sectional configuration to facilitate a controlledbuckling function. In other aspects of the invention the load-bearingsurface has a substantially elliptical cross-sectional configuration ora substantially rectangular cross-sectional configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of one aspect of the cushion;

FIG. 2 is a front perspective view of the support surface;

FIG. 3 is a front plan view of a section of the support surfaceillustrating the placement of the self-adjusting valve;

FIG. 4 is a side elevational view of the self-adjusting valve;

FIG. 5 is a bottom plan view of a support surface;

FIG. 6 is a perspective view of the cover top;

FIG. 7 is a bottom plan view of the assembled cushion;

FIG. 8 is a perspective view of an optional top air pad;

FIG. 9 is a cross sectional view of one embodiment of a self-adjustingvalve, wherein the valve comprises an axial labyrinth seal design;

FIG. 10 is a cross-sectional view of another embodiment of aself-adjusting valve, wherein the valve comprises a radial labyrinthseal design; and

FIG. 11 is a cross-sectional view of another embodiment of aself-adjusting valve, wherein the valve comprises an expansion valvedesign.

DETAILED DESCRIPTION

One aspect of the cushion is indicated generally by numeral 20 inFIG. 1. It will be understood that the term cushion, as used herein, isintended to include cushions for seating, larger embodiments oftenreferred to as mattresses or mattress overlays, pillows or any othersuch support surfaces for supporting the anatomy of a user.

Cushion 20 comprises a support surface 22, a cover bottom 24 a cover top26 and a valve 28. Referring to FIG. 2, support surface 22 comprises aresilient pad having anterior section 30 and a posterior section 32.Generally, the anterior and posterior sections of the support surfaceare formed from a compressible, resilient material such as polyurethanefoam. In general, posterior section 32 may be formed from stiffer foamthan anterior section 30 such that posterior section 32 will have agreater restoring force than the anterior section. In most situations,the posterior section of a cushion supports at least fifty percent (50%)of the seated user's body weight. A firmer posterior section providesmore support and a feeling of greater stability. The support surfaceconstruction is such that the cushion will not bottom out under a seateduser. It will be understood that support surface 22 can be a single orunitary piece as well.

The anterior wall 33 of the support surface defines a cavity 34 forhousing valve 28, as will be described below. Both anterior section 30and posterior section 32 comprise a plurality of cells or suspensionelements 35 arranged in lateral and transverse rows across the expanseof the sections, as seen in FIG. 5. It will be understood that thesupport surface, whether a single piece or comprising an anterior orposterior section is made, and functions, in accordance with theprinciples disclosed in the assignee's U.S. Pat. No. 7,424,761 and7,681,264, both of which are incorporated herein by reference.

In one aspect, each suspension element 35 has a displaceable,load-bearing surface 36, a first end wall 38 and a second end wall 40.The load bearing surface, end walls define an inner chamber 42. Chambers42 can be empty or filled, for example, with foam or other material tochange the support characteristics of the cushion or the air egress andingress characteristics of the cushion. Moreover, chamber 42 can have athin wall or skin over them with a small hole in the wall to vary orcontrol the compression characteristics by controlling the fluid flowfrom the chamber under force. In one aspect, the material thickness ofthe load-bearing surface 36 is greater than the material thickness ofthe end walls so that the end walls can distend outwardly when force isapplied to the load-bearing surface.

The load bearing surfaces 36 cooperate to form a displaceable surfacethat, when deformed, exerts a restoring force that is generally constantirrespective of the extent of the deformation. Support pad 22 applies agenerally uniform supporting pressure against an irregularly contouredbody supported on the cushion. In one aspect of the invention the arrayof suspension elements is arranged in a pattern wherein the longitudinalaxis of each suspension element is positioned at a right anglerelationship to the longitudinal axis of the adjacent suspensionelements. The right angle axis position of the suspension elementsimproves stability imparted to the user.

In one aspect of the invention the load-bearing surface 36 has agenerally arch-like cross-sectional configuration to facilitate acontrolled buckling function. In other aspects of the invention theload-bearing surface can have a substantially elliptical cross-sectionalconfiguration or a substantially rectangular cross-sectionalconfiguration. In another aspect of the support surface where thearch-like or elliptical suspension elements 35 have the displaceableload-bearing surface 36 down, a web-like membrane of compressibleresilient material 37 between suspension elements 35 prevents thesuspension elements from splaying at the user interface of the supportsurface under the seated user.

In the illustrated embodiment there is cover top 26 that covers the topsurface of support pad 22 as well as cavity 34 and provides openings 43for valve 28 in fluid communication with the atmosphere, as seen in FIG.6. Cover top 26 generally can be a vacuum formed polyurethane filmhaving a thickness of about 0.020 inches in the exemplary embodiment. Inanother embodiment, the cover top can have a fabric bound to thepolyurethane film, providing a cover top over the support surface thatis easily cleaned by wiping down with a mild cleaning solution. In analternative embodiment the cover top can have a plurality of small holestherein, with one hole positioned over each cell chamber 42 or selectcell chambers and a top air pad 44 with opening 43, as seen in FIG. 8,having individual air pads 46 of vacuum formed plastic can be positionedover the support surface. One aspect of the top air pad 44 includes thearray of individual air cell pads 46 in fluid communication with thesupport surface to reduce friction and shear at the user interface ofthe support surface under the seated user.

A cover bottom 24, as seen in FIG. 7, having a configurationcomplementary to the suspension elements generally comprises vacuumformed plastic film, as well, having a thickness of about 0.020 inchesin an exemplary embodiment. Cover bottom 24 duplicates the configurationof the suspension elements 35, as at 47, which seats the suspensionelements. This arrangement reduces the volume of the cushion and,therefore, reduces the amount of air within cushion 20, making theexpulsion of air easier to control. It also eliminates the usersensation that the cushion feels like a balloon. This arrangement alsoprevents or controls splaying of the suspension elements under load.Cover top 26 and cover bottom 24 can be joined together, either bysonic, RF welding, gluing or other appropriate means sealing themtogether around the edges of the cushion with support pad 22 inside. Thecushion then is impervious to gas or fluids.

The cushion can have any desired configuration, with the illustratedembodiment being a rectangle. The dimensions of cushion 20 can varydepending upon the size of the surface on which it will be used ordepending upon the size of the user. A cushion having dimensions ofeighteen (18) inches by eighteen (18) inches is one representativeembodiment. A larger, heavier user would employ a cushion having greatersurface area so as to spread the seated user's body weight over a largersurface area and thereby controlling the fluid pressure within thecushion and the restoring force against the seated user's body. Bycontrolling the surface area and the spring compression of the valve, aswill be explained below, an optimum pressure of about 40 to about 50mmHg within the cushion can be achieved.

It will be noted that when support pad 22 is compressed by the weight ofa seated user, the inner chambers 42 and the polyurethane foam itselfwill expel air. Since the support pad 22 is sealed within the topcovering and bottom, air can only escape through valve 28 and opening 43to allow the cushion to deform and the user to be immersed into thecushion. Hence, seating and positioning characteristics, includingimmersion, can be controlled by controlling the egress of air out ofvalve 28, as will now be explained.

Valve 28 is positioned in cavity 34 and is in fluid communication withthe interior of the cushion in any acceptable manner. For example, valve28 can be in fluid communication with a conduit 48 that extends intocavity 34. Alternative, valve 28 can be in fluid communication with theinterior of the cushion though a hole in the cushion top covering,bottom covering or any other structure so as to be in fluidcommunication with the interior of the cushion. A separate conduit isnot required.

In a preferred embodiment, valve 28 comprises a labyrinth seal designthat dampens dynamic air flow and pressure spikes. In general, aftpressure from cushion 20 with a seated user causes the valve ball toclose against the spring compression force in the valve body. Thedynamic air pressure resulting from movement of the seated user isdampened by using of a labyrinth multistage pressure reductionconfiguration. Moreover, the compression force of the spring can bevaried to get optimal seating characteristics.

FIGS. 9 through 11 are cross-sectional schematics of variousconfigurations of valve 28, referred to as valves 28A, 28B and 28C inthe respective drawings. Referring to FIG. 9, valve 28A has a casing 49with an elongated extension 50. Casing 49 can be of any configuration,however, a cylindrical, circular or disk-like configuration works well,as seen in FIGS. 3 and 4. Extension 50 can be tubular with an internalbore 52. Circumferential barb 54 functions to secure the extensionwithin conduit 48. Conduit 48 is in fluid communication with theinterior of the cushion and, hence, bore 52 and valve 28 are in fluidcommunication with the interior of the cushion.

Bore 52 also is in fluid communication with a labyrinth inside the valvecasing. For example, air flow from the interior of the cushion follows apath shown by arrows A1. At stricture 57 the fluid flow is constricted;there is a significant pressure drop as the fluid flow expands intochamber 58; again there is constriction at stricture 59 and a pressuredrop at chamber 60. There is a third constriction of flow at stricture62 and a pressure drop at chamber 64. Ultimately, the reduced fluid flowcontacts valve ball 66. Valve ball 66 is biased in a closed positionagainst valve seat 67 by valve spring 68. It will be understood that aslong as valve ball 66 is biased against valve seat 67, no air willescape through the valve. However, when a predetermined fluid pressureresulting from the user sitting on cushion 20 is applied against thevalve ball by the air flow, valve ball 66 is urged away from valve seat67 and air will escape from valve 28 through exhaust port 69.

Valve spring 68 has preselected compression force depending upon thesurface area of the cushion and the estimated weight of the user. Thevalve spring is selected so that sufficient air escapes the cushionresulting in emersion into the cushion until the user's anatomy is aboutone-half (½) to (1) inch from the surface on which the cushion isposition, for example, a wheelchair seat. Also, valve spring 68 isselected so that the fluid pressure within the cushionis about 40 toabout 50 mm Hg, resulting in a uniform restoring force against theseated user's body.

Since valve 28 comprises the labyrinth configuration, the step down inpressure is such that the force required to open the valve is greatestwhen the user at first sits on the cushion and begins to immerse thebuttocks and ischial area into the cushion. This generally constantforce on the cushion generates pressure within the cushion the fluidpressure within the cushion and the restoring force against the seateduser's body allows the valve spring 68 to overcome the fluid pressureand close the valve, maintaining the appropriate or desired immersiondepth. Once the user is seated, the pressure reducing labyrinthconfiguration within the valve keeps air from leaking under dynamicpressure changes that may result from user movement. In any event, thevalve spring is such that it will keep the valve closed and not allowthe user to bottom out.

Valve 28 includes an inflation valve, indicated generally by referencenumber 70 which, in a preferred aspect, comprises air ports 72 in fluidcommunication with the atmosphere. Inflation valve 70 includes a flap 74comprising a somewhat flexible but durable material such as silicon,Teflon® or the like, which seals ports 72 under pressure from withinvalve 28. However, when the user is off the cushion, the atmosphericpressure, which then is generally greater outside the cushion thanwithin, causes air to flow through ports 72 and into the cushionfollowing a path shown by arrows A2, aided by mechanical drawing in ofair by the foam within the cushion as a changes from a compressed tonon-compressed state.

Valve 28B is illustrated in FIG. 10. Valve 28B is constructed verysimilarly to valve 28A. Valve 28B includes a casing 49 with an extension50 having an internal bore 52 and circumferential external barb 54. Bore52 is in fluid communication with the interior of the cushion and alabyrinth inside the valve casing. Air flow from the interior of thecushion follows a path shown by arrows A1. At stricture 57 the fluidflow is constricted with a pressure drop at the fluid flow expands intochamber 58; there is constriction at stricture 59 and a pressure drop atchamber 60. There is a third constriction of flow at stricture 62 and apressure drop at chamber 64. Valve 28B includes a valve ball 66, valveseat 67, valve spring 68 and exhaust port 69 that that function in thesame manner set out above in regards to valve 28A.

Valve 28B also includes an inflation valve, indicated generally byreference number 70 which comprises air ports 72 in fluid communicationwith the atmosphere. Inflation valve 70 includes a flap 74, which sealsports 72 under pressure from within valve 28. Air flows in through ports72 and into the cushion, following a path shown by arrows A2, asexplained above.

Valve 28C is illustrated in FIG. 11. Valve 28C is constructed verysimilarly to valves 28A and B. Valve 28C includes a casing 49 with anextension 50 having an internal bore 52 and external barbs 54. Bore 52is in fluid communication with the interior of the cushion and theexpansion chambers inside the valve casing. Air flow from the interiorof the cushion follows a path shown by arrows A1. At orifice 57 thefluid flow is constricted and a pressure drop as the fluid flow expandsinto chamber 76; there is constriction at orifice 77 and a pressure dropat chamber 78. Valve 28C includes a valve ball 66, valve seat 67 andvalve spring 68 and exhaust port 69 that function in the same manner setout above in regards to valve 28A.

Valve 28C also includes an inflation valve, indicated generally byreference number 70 comprises air ports 72 in fluid communication withthe atmosphere. Inflation valve 70 includes a flap 74 which seals ports72 under pressure from within valve 28C. Air flows in through ports 72and into the cushion following a path shown by arrows A2, as explainedabove.

It will be understood that the valves described can be employed incushions or mattresses of designs different from the cushion illustratedherein. The valve can be constructed so as to accommodate users ofdifferent sizes. The fluid flow characteristics can be varied by the useof different springs or a different labyrinth seal clearances ororifices. The valve can be used in a cushion that provides optimalseating characteristics without manipulation. The user rests on thecushion and the self-adjusting valve adjusts so that the cushion hasoptimum immersion and restoring force characteristics.

1-18. (canceled)
 19. A cushion comprising: a support surface comprisinga plurality of compressible suspension elements, and a valve in fluidcommunication with the plurality of compressible suspension elementshaving internal labyrinth structures that provide a controlled expulsionof air from the cushion to dampen air flow until a user positioned onthe cushion is optimally immersed in the cushion and control pressurespikes caused by movement on the cushion.
 20. The cushion of claim 19wherein the valve comprises an expansion valve.
 21. The cushion of claim19 wherein the valve comprises a pressure responsive compression spring,said compression spring having a predetermined compression force thatcontrols the expulsion of air from the cushion corresponding to adesired immersion depth of the user.
 22. The cushion of claim 19 furthercomprising a cover having a top and a bottom, the bottom configuredcomplementary to the suspension elements to control splaying of thesuspension elements under load.
 23. The cushion of claim 22 wherein thecover top comprises vacuum formed polyurethane.
 24. The cushion of claim19 wherein the support surface comprises a anterior section and aposterior section comprising polyurethane foam, said posterior sectionhaving a greater restoring that the anterior section.
 25. The cushion ofclaim 24 wherein said anterior section of the support surface has acavity formed therein to house the valve.
 26. The cushion of claim 19wherein the compressible suspension elements are inflatable air cells.27. The cushion of claim 19 wherein the valve further comprises: a valveseat, a valve ball positioned adjacent the valve seat, and a bias springfor biasing the valve ball against the valve seat to close the valve.28. The cushion and valve of claim 19 wherein the labyrinth structurescomprise a labyrinth seal that dampens air flow and pressure spikes atthe valve ball.
 29. The cushion and valve of claim 19 wherein the valvefurther comprises an inflation valve in fluid communication with theatmosphere to allow expansion of the compressible suspension elements.30. A valve for a cushion having compressible suspension elements,comprising: a valve ball and pressure responsive compression springhaving a predetermined compression force that controls expulsion of airfrom the cushion corresponding to a desired immersion depth of a user,and a labyrinth structure in fluid communication with the compressiblesuspension elements and the valve ball that dampens dynamic air flow andpressure spikes against the valve ball.
 31. The valve of claim 30further comprising inflation valve structures that allow an ingress ofair into the suspension elements when load is removed from the cushion.